1. Field of the Invention
The present invention relates to an image forming apparatus in which an electronic photographing system is adopted, and in particular to an image forming apparatus in which improvements are added to a fixing mechanism thereof to fix toner images formed on a sheet of paper via processes of photosensing, development and transfer.
2. Description of the Prior Art
In the image forming apparatus of electronic photographing system, image formation is completed by fixing toner images formed on a sheet of paper such as a transfer paper by the preceding processes. The fixing is carried out by passing a sheet of paper, on which toner images are formed, between a heating roller and a pressure roller to cause toner to be heated and melted.
FIG. 5 shows the outline configuration of a fixing mechanism 15 according to a conventional example of the above image forming apparatus, and the fixing mechanism consists of a heating roller 10 to heat a sheet of paper on which toner images transferred from the preceding process are formed and to cause the toner to be melted, a pressure roller 11 to compress the sheet of paper in cooperation with the heating roller 10, and a fixing felt 12 contacted with pressure to the surface of the heating roller 10, which gives a coat of oil onto the heating roller 10 and cleans it up.
In the conventional fixing mechanism 15, foreign matters and duct on the surface of the heating roller 10 are obliged to be accumulated at the position where the heating roller 10 is brought into contact with the fixing felt 12, and paper dust and toner residues are gradually accumulated upstream in the rotation direction at the position where the fixing felt 12 is brought into contact with the surface of the heating roller 10. There is such a problem that, as such foreign matters and residues are increased, they may easily drop on sheets of paper to cause them to be stained.